1. Field of the Invention
The present invention relates to restraint systems in vehicles, and in particular to inflatable "air bag" systems deployable from outboard armrests on vehicle seats.
2. Discussion of the Prior Art
Inflatable air bags used to protect vehicle occupants during a collision are well known in the art of restraint systems. Typically, these devices are located in the steering wheel or instrument panel and deploy in the event of frontal collision.
It has also been previously proposed to locate air bags on the outboard side of vehicle occupants to absorb energy during a side impact, or during a collision having at least a lateral component. Various mounting locations have been proposed, including locating the air bag in the back rest portion of the seat, the seat bottom, a door panel, a door mounted armrest, or in the vehicle roof above the door. From these positions, the air bag is able to inflate in the area between the occupant and the door.
During a collision of sufficient energy, a impact sensor triggers a gas generator which rapidly inflates the air bag. Because the air bag must fill so rapidly in order to protect the occupant, its operation is essentially a contained explosion. As such, injuries can occur to the occupant, aside from the collision itself, when the air bag is normally deployed. In designing air bag systems, a balance must be struck between ensuring that the air bag deploys quickly enough to protect a vehicle occupant during a high speed collision, and reducing the risk of injury due to a rapidly inflating air bag.
The design challenge becomes more difficult for side impact air bag systems. Compared to a frontal impact, there is very little time or distance between a side impact and intrusion upon the occupant. Unlike a frontal impact, there is essentially no time or distance for energy to be absorbed in crumple zones of the vehicle or for the impact to travel through the vehicle structure before reaching the occupant. An air bag must inflate even more rapidly in a side impact than in a frontal impact in order to cushion the occupant from the impact and help protect against physical intrusion into the seating area. This is also much less room beside an occupant to deploy an air bag, as opposed to in front of a seated occupant. Therefore, side impact air bags inherently afford less protection from collision and greater exposure to deployment injuries than do standard air bags for frontal collisions. Because of this, side impact air bag location and deployment direction are critical design criteria.
Air bags located in door armrests or panels have a number of drawbacks. These types of configurations typically require the air bag to deploy directly toward the occupant's head or torso, much like a front mounted air bag, but with less distance between the stowed air bag and the occupant and less time for deployment. This increases the risk of injury due to deployment.
In order to protect the occupant's head during a collision, a separate air bag must deploy from the roof or alternatively the arm rest mounted air bag must extend from the occupant's lower torso up to his or her head when the air bag is inflated. This long distance requires more inflation time and or a more violent burst of gas to inflate, also increasing the risk of injury.
When extending up towards the occupant's head from the armrest, the air bag may snag or get caught up in the seat, the occupant, or his or her clothing. A more forceful inflation may be required to insure that the air bag fully extends in the narrow area between the occupant and the door. In this configuration, the air bag inflates into the side of the occupant's lower rib cage. This violent explosion of the expanding air bag not only poses a danger to the rib cage, but also pushes the occupant's outside arm upward, which can also cause a serious injury or affect the full deployment of the air bag.
Another problem associated with an air bag mounted in the door armrest or panel is its inability to remain optimally positioned between the occupant and the door or side of the vehicle. Because the occupant typically can adjust the seat in a variety of directions, the air bag must be made larger to cover all of the possible seat positions. Otherwise, extremities of the occupant will not be protected in certain seat positions. Even with a larger air bag, the cushioning may not be accurately focused on the occupant, and the above mentioned problems such as deployment time, deployment force, and snagging are exacerbated.
An air bag mounted in a door armrest is also susceptible to displacement during a collision. When a second vehicle intrudes into the door structure of the first vehicle, the position or orientation of the air bag in the door of the first vehicle may be disrupted enough to cause improper deployment of the air bag. For instance, the air bag may be pushed into the vehicle or even into the occupant's outer side before it can properly deploy.
Some of the above problems can be solved by locating the side impact air bag in the seat back or bottom cushion. In these locations the air bag moves with the occupant when the seat is adjusted so the air bag remains optimally focused on the occupant and does not have to be any larger than necessary. The air bag is also farther away from the impact, giving it more time to deploy. However, in these locations the air bag is deployed directly adjacent to the occupant, increasing the risk of injury. The possibility of objects interfering with proper air bag deployment is also a problem. During an accident, the occupant may block or partially obstruct the initial deployment of the air bag, or it may become snagged on the seat, armrest, interior door surface or restraint belt. Also, when the air bag is mounted in the seat bottom, it has a longer distance to travel to become fully deployed than an air bag mounted in a door armrest or panel.
What is needed, and is lacking in the prior art, is a side impact air bag system which deploys the air bag from a location central to the occupant, a location that remains centrally focused on the occupant even when the seat position is shifted, and deploys in such a manner that both the risk of injury due to deployment and the possibility of the air bag snagging on the occupant or adjacent objects are minimized.